Sandbox Reserved 811: Difference between revisions
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= '''Na+,K+ ATPase''' = | |||
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= α-subunit = | == α-subunit == | ||
The α-subunit is a 1021 residues and 112 kDa polypeptide. | The α-subunit is a 1021 residues and 112 kDa polypeptide. | ||
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[[Image:3B8E 2D view.jpg|thumb|Architecture of the Na+,K+-ATPase αβγ-complex, with its K+/Rb+ sites.|450px]] | [[Image:3B8E 2D view.jpg|thumb|Architecture of the Na+,K+-ATPase αβγ-complex, with its K+/Rb+ sites.|450px]] | ||
== Fixation of cations == | === Fixation of cations === | ||
These domains A, N, P are along the Na+ and <scene name='56/568009/Cation_binding_sites/1'>K+ binding residues</scene>. Indeed, two sites, which bind 2K+ or 2Na+, locate between helices 4, 5 and 6. The third Na+ is bound on the carboxyl-terminal domain. | These domains A, N, P are along the Na+ and <scene name='56/568009/Cation_binding_sites/1'>K+ binding residues</scene>. Indeed, two sites, which bind 2K+ or 2Na+, locate between helices 4, 5 and 6. The third Na+ is bound on the carboxyl-terminal domain. | ||
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== Post-translational modifications == | === Post-translational modifications === | ||
It seems that post-translational modifications modulate the activity of the enzyme. Indeed the phosphorylation on Tyr 10 modulates pumping activity. The phosphatase 2A (PP2A) dephosphorylates this residue when there is an increase in intracellular Na+. This dephosphorylation allows to increase the catalytic activity. | It seems that post-translational modifications modulate the activity of the enzyme. Indeed the phosphorylation on Tyr 10 modulates pumping activity. The phosphatase 2A (PP2A) dephosphorylates this residue when there is an increase in intracellular Na+. This dephosphorylation allows to increase the catalytic activity. | ||
= β-subunit = | == β-subunit == | ||
The β-subunit is a glycoprotein of 35 kDa and made of 302 residues. The hydrophilic part of the β-subunit is exposed only on the outer surface of the cell. It is a glycosylated domain which covers the α-subunit in order to prevent the escape of K+ ions. | The β-subunit is a glycoprotein of 35 kDa and made of 302 residues. The hydrophilic part of the β-subunit is exposed only on the outer surface of the cell. It is a glycosylated domain which covers the α-subunit in order to prevent the escape of K+ ions. | ||
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The cytosolic N-term of β subunit continues probably aroud the α subunit, but cannot be modelled. The first residues of the β-domain can establish a contact with the αM7-αM8 loop aroud the SYGQ motif which seems indispensable for αβ assembly. | The cytosolic N-term of β subunit continues probably aroud the α subunit, but cannot be modelled. The first residues of the β-domain can establish a contact with the αM7-αM8 loop aroud the SYGQ motif which seems indispensable for αβ assembly. | ||
= γ-subunit = | == γ-subunit == | ||
Certain pumps are made of a third subunit, γ, which plays a role in the regulation of tissue-specific pumping activity. It owns a transmembrane domain, γM, made of an approximately 30 amino acids α-helix, which interacts with the α-subunit. Indeed, Glu 953 of αM9 interacts with Gly 41 of γM, which is found mutated to arginine in familial dominant renal hypomagnesaemia. Phe 949, Leu 957 and Phe 960 of αM9 interact with other residues of the γ-subunit. | Certain pumps are made of a third subunit, γ, which plays a role in the regulation of tissue-specific pumping activity. It owns a transmembrane domain, γM, made of an approximately 30 amino acids α-helix, which interacts with the α-subunit. Indeed, Glu 953 of αM9 interacts with Gly 41 of γM, which is found mutated to arginine in familial dominant renal hypomagnesaemia. Phe 949, Leu 957 and Phe 960 of αM9 interact with other residues of the γ-subunit. | ||